Radial layout for acoustic wave touch sensor

ABSTRACT

Surface acoustic waves in a radial pattern are used to detect touch. Different radial transducer arrangements may allow for locating multiple simultaneous touches without ambiguity. Instead of transmitting along a line to be reflected at multiple points, the surface acoustic waves are transmitted radially. The surface acoustic waves are transmitted along different angles in an angular span spread out over at least part of the touch region. Using acoustic waves traveling along intersecting paths, a point location of a touch may be determined by detection, in part, of at least one angle.

BACKGROUND

Touch sensors detect touch, such as from a user's finger, a stylus, orsome other object. Touch sensors may be transparent or opaque inputdevices for computers or other electronic systems. A transparent touchsensor, such as a touchscreen, may be used in conjunction with a displaydevice. Touch displays are increasingly used in commercial applications,such as restaurant order entry systems, industrial process controlapplications, interactive museum exhibits, public information kiosks,pagers, cellular phones, computers, personal digital assistants, andvideo games.

Acoustic-based sensors may be used to detect touch. Certain types ofacoustic touchscreens, also known as ultrasonic touchscreens, detecttouch with high transparency and high resolution, while providing adurable touch surface. Of particular commercial interest are ultrasonictouchscreens using surface acoustic waves. FIGS. 16A and 16B show anexample of a conventional wedge transducer 26 for generating surfaceacoustic waves that all propagate in a direction represented by arrow 5.A piezoelectric element 30 mounted on the top back surface (alsoreferred to as a first surface) of the wedge generates bulk pressureacoustic waves, represented by rays, in the wedge 28. At the boundarysurface of the wedge 28 that is on or in contact with the touchsubstrate 10, surface acoustic waves, represented by ray 5, aregenerated that propagate across the touch substrate 10.

A surface acoustic wave touchscreen includes a substrate on which thesurface acoustic waves propagate. X and Y transducers generate surfaceacoustic waves along perpendicular axes. Transmit reflective arraysproximate the edges of the touch substrate and spaced along the axesreflect the transmitted surface acoustic waves across the touchscreen'stouch surface along perpendicular paths. Receive reflective arraysproximate the edges of the touch substrate and spaced along oppositesides from the transmit reflective arrays reflect the surface acousticwaves that have propagated across the touch surface to X and Y receivetransducers or sensors. These reflective arrays may be referred to as“linear reflective arrays”, and acoustic waves traveling in a lineardirection partially pass through the linear reflective array andpartially are reflected by the linear reflective array in a directionnormal to the linear direction. When a touch occurs on the touchsurface, the touch causes attenuation of the surface acoustic waves atcorresponding locations along the two axes, X and Y. The X, Y touchposition is determined based on the timing of the attenuation in thesignal received at the receive sensors.

With some conventional surface acoustic wave touch sensors, multiplesimultaneous touches may be difficult to correctly locate due toambiguity. The multiple touches cause the detection of two X and two Yattenuation coordinate locations, so that it may be unclear whichdetected X location is associated with a particular detected X, Ylocation. Associating the correct combination of X and Y locationstogether to determine the proper coordinates requires a guess or moreinformation.

SUMMARY

In a first aspect, a touch sensor is provided for detecting a touch. Atouch substrate has a top surface and a bottom surface. The top surfacehas a touch region. A first transducer is provided for generating firstsurface acoustic waves on the touch region. The first transducer is afirst radial transducer. A second transducer is provided for receivingthe first surface acoustic waves. The first surface acoustic waves havea first radial pattern with an angular span of at least 20° in the touchregion. The first radial pattern is divergent as a distance from thefirst transducer increases. A third transducer is provided forgenerating second surface acoustic waves on the touch region. The secondacoustic waves intersecting in the touch region the first surfaceacoustic waves.

In a second aspect, a method is provided for detecting a touch on asurface. A first acoustic fan is generated with non-parallel propagationover the surface in an area for the touch. A first angle associated withthe touch is detected from attenuation of the first acoustic fan along afirst radial line. A point location of the touch is determined as afunction of the first angle.

In a third aspect, a touch sensor is provided. A first radial transduceris on a substrate. The first radial transducer is configured to generatefirst surface acoustic waves on the substrate along different radiallines separated by an angle of at least 20° in a touch region. One ormore first receive transducers are operable to receive the first surfaceacoustic waves along the different radial lines. A second transducer ison the substrate. The second transducer is configured to generate secondsurface acoustic waves on the substrate along parallel lines. A firstlinear reflective array is configured to reflect the second surfaceacoustic waves from the second transducer in a parallel pattern in thetouch region. One or more second receive transducers are configured toreceive the second acoustic waves from the parallel pattern.

The present invention is defined by the following claims, and nothing inthis section should be taken as a limitation on those claims. Furtheraspects and advantages of the invention are discussed below inconjunction with the preferred embodiments and may be later claimedindependently or in combination.

BRIEF DESCRIPTION OF THE DRAWINGS

The components and the figures are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the invention.Moreover, in the figures, like reference numerals designatecorresponding parts throughout the different views.

FIG. 1 is an example general diagram of a touch surface in top view witha radial transducer for generating radial surface acoustic waves;

FIG. 2 is a cross-sectional view of the example touch surface and radialtransducer of FIG. 1, according to a specific embodiment;

FIG. 3A shows one embodiment of a radial transducer with a convex wedge,and FIG. 3B shows the transducer of FIG. 3A in an example use forradially propagating surface acoustic waves mounted on back of asubstrate;

FIGS. 4-8 illustrate other embodiments of radial wedge transducers withvarying configurations of wedges for radial transmission;

FIG. 9 shows an embodiment of an interference structure on a linearwedge transducer for generating radial surface acoustic waves;

FIG. 10 shows a cross-sectional and two perspective views of a radialtransducer with a curved piezoelectric for generating radial surfaceacoustic waves, according to a specific embodiment;

FIG. 11 illustrates a top view of generation of radial surface acousticwaves by reflection of waves from a linear wedge transducer from acurved reflector, according to a specific embodiment;

FIG. 12 shows top and bottom views of a part of a touch substrate usinga curved corner for generating surface acoustic waves in a radialpattern, according to a specific embodiment;

FIG. 13 illustrates curved surface features, such as a grating, comb, orinterdigital transducer, for generating surface acoustic waves in aradial pattern, according to a specific embodiment;

FIG. 14 is a top view of a linear wedge transducer with a lens forgenerating surface acoustic waves in a radial pattern, according to aspecific embodiment;

FIG. 15 is a flow chart diagram of one embodiment of a method forgenerating radial surface acoustic waves;

FIGS. 16A and 16B are perspective and side views of a conventionallinear wedge transducer;

FIG. 17 is a top view diagram of a touch surface layout using a radialpattern according to one embodiment;

FIG. 18 is a top view diagram of an embodiment of a touch sensor layoutwith a radial pattern for a triangular touch region;

FIG. 19 is a top view diagram of an embodiment of a touch sensor layoutwith a radial pattern for a rectangular touch region;

FIG. 20 is a top view diagram of another embodiment of a touch sensorlayout with a radial pattern for a rectangular touch region;

FIG. 21 is a top view diagram of an embodiment of a zero-bezel touchsensor layout with a radial pattern for a triangular touch region;

FIG. 22 is a flow chart diagram of one embodiment of a method fordetecting one or more touches with a radial wave pattern;

FIG. 23 is a top view diagram of yet another embodiment of a touchsensor layout with radial patterns for a rectangular region;

FIG. 24 is a top view diagram of one embodiment of part of a touchsensor layout with a radial pattern for detecting radius based onattenuation width; and

FIG. 25 is a top view diagram of one embodiment of part of a touchsensor layout with a radial pattern for detecting radius based onattenuation width for comparison with FIG. 24.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Radially transmitted or received surface acoustic waves may be used fortouch sensors used in zero-bezel product designs, multiple touchsensors, or other uses. The fanned out beam or radial wave pattern isgenerated by a surface acoustic wave generator. The transducer of thesurface acoustic wave generator may be positioned on a back or frontside of a touch surface. In cases surface acoustic waves are desired tofully illuminate or propagate over the desired touch area, radiallytransmitted or received surface acoustic waves may complete the desiredcoverage of the touch area with touch sensitive surface acoustic waves.By using multiple such fanned out beams, ambiguity for multiple touchesmay be avoided while still sensing touches at the periphery of the touchsurface. Different embodiments are provided for a surface acoustic wavegenerator or receiver of a fan beam. A convex wedge transducer mayproduce a radial or fanned out beam. For example, the wedge of theradial wedge transducer is modified so that the piezoelectric element ismounted on the wedge front surface and so that a curved back surface ofthe wedge functions as a curved focusing mirror or reflection surface toreflect bulk pressure waves propagating in the wedge material. Asanother example, a linear wedge is modified with a pattern of slotsdesigned in the surface that bonds to the glass, creating interferenceto fan out the generated surface acoustic waves. In another example, awedge transducer generates a generally focused or linear wavefront, butanother device spreads or fans the wavefront. Such other devices includean acoustic lens (e.g., a glass frit lens), a rounded glass edge, or acurved reflector. In yet another example, a curved piezoelectric elementgenerates a divergent wavefront in the wedge, resulting in divergingsurface acoustic waves.

In a conventional wedge transducer, a “wedge” serves to couplevibrations of a piezoelectric element to surface acoustic wavespropagating a substrate surface. In a conventional wedge transducer,this element that couples piezoelectric element vibrations and surfaceacoustic waves indeed has a geometry approximating a wedge shape. In thefield, it has become common and concise to use the term “wedge” for thiscoupling element. In radial wedge transducer design, such a couplingelement may be termed a “wedge” even in cases where the “wedge” nolonger has a wedge shape.

In other embodiments, the surface acoustic wave generator for radialwaves does not include a wedge. For example, a grating of curved linesgenerates surface acoustic waves in a radial pattern in response toimpinging waves transmitted through the touch substrate from apiezoelectric element. As another example, a comb of curved linesgenerates surface acoustic waves in a radial pattern in response towaves transmitted from a piezoelectric element in contact with the comb.In yet another example, a piezoelectric film with curved interdigitalelectrodes generates the surface acoustic waves in the radial pattern.

FIG. 1 shows an example general diagram of a touch sensor arrangement. Atouch surface 12 includes a radial surface acoustic wave generator 14 orradial acoustic transducer for generating (and/or receiving) surfaceacoustic waves 18 (shown with solid line arrows) in a radial patternover a touch region 16. Additional components may be provided. Forexample, additional surface acoustic wave generator 14 and/or reflectivearrays and acoustic receive transducers (not shown) are provided forsensing touches from interference with the surface acoustic waves 18. Insome embodiments, the surface acoustic wave generator 14 may include alinear transducer for generating a surface acoustic wave along a singleline for reflection over the touch region 16.

FIG. 1 represents the surface acoustic waves 18 as rays. Such raytracing is an approximation of acoustic wave propagation. A completeunderstanding of various second order effects in the design and use ofradial surface acoustic waves may extend beyond the ray tracingapproximation. Such considerations for the fan beam or radial patternand propagation may be used. In general, the radial wave pattern(regardless of whether the waves are being propagated away from thetransducer or toward the transducer) diverges as the distance away fromthe transducer increases. Much of the context of discussion and thefigures show the rays or surface acoustic waves propagating away fromthe acoustic wave generator 14, representing transmission or transmitoperation. Of course it should be understood that the same or similarradial transducer design or layout may be used in a receive mode. Toillustrate receive mode operation, the direction of the arrows or raysis reversed. Any of the transmit or receive operation, layout, orcomponents discussed below may alternatively be used in the other ofreceive or transmit operation, layout, or components.

The touch surface 12 is the surface of a substrate 10, such as a glassplate in a specific embodiment. Other materials may be used, such asmetal, ceramics or polymer-based materials with sufficiently lowultrasonic attenuation. The touch surface 12 is smooth or flat or gentlycurved to allow propagation of surface acoustic waves over the touchregion 16. The touch surface 12 is free of bumps, divots, ridges, orother structures interfering with propagation of surface acoustic waves.In some embodiments, coversheets may be used on top of the plate to forma composite structure of a SAW absorbing coversheet, a small separatingair gap that is eliminated at the location of a touch, and a “substrate”capable of propagating surface acoustic waves. In alternativeembodiments, such structures are provided on the touch surface 12 in ornot in the touch region 16.

As shown in FIGS. 1 and 2, the touch surface 12 is on a flat slab orsubstrate 10 with a rectangular shape. Other shapes may be provided,such as circular, square, triangular, or irregular. Rather than beingflat, the top 20 and/or bottom 22 of substrate 10 may be curved, wavy,or other non-flat shape. For example, the top surface 20 with the touchregion 16 is on a hemisphere or other track ball or mouse shape. Auniform or non-uniform thickness is provided, provided the thickness ofsubstrate 10 is several times greater than the wavelength of thepropagating surface acoustic wave.

A connecting surface 24 surrounds and connects the top and bottomsurfaces 20, 22. The connecting surface 24 may be flat (straight) orrounded according to different specific embodiments. For example, theconnecting surface 24 is rounded without a ridge or sudden transition sothat surface acoustic waves may travel from the bottom surface 22 to thetop surface 20 and corresponding touch region 16. As another example,the connecting surface 24 has a corner or other sharp transition withthe top surface 20 to reflect surface acoustic waves. Different portionsof the connecting surface 24 may have different characteristics, such asa corner or ends being rounded or flat and the rest of the connectingsurface 24 being the other of flat or rounded.

In one embodiment, the connecting surface 24 is curved (in plan view)and the surface acoustic wave generator 14 is on the bottom surface 22.The curve spreads the surface acoustic waves. Generated surface acousticwaves travel over the rounded edge connecting surface 24 onto the topsurface 20. With acoustic receivers positioned on the back surface 22 aswell, there is no need for a bezel to protect the perimeter of the topsurface 20 of the substrate, thus enabling zero-bezel product designs.In alternative embodiments shown in FIGS. 1 and 2, the transducer 26 ison the top surface 20, such as in a region for overlay of a bezel.

The touch region 16 is defined by the locations at which touches may besensed based on perturbations of surface acoustic waves or wavefrontswith sufficient magnitude or energy above a noise level to be detected.The touch region 16 is of any size and shape. For example, the touchregion 16 includes a rectangular, circular, triangular or other shapeover which surface acoustic waves propagate. The location of the receivereflective arrays (e.g., a line array of reflector elements on the topsurface 20 at X and Y periphery edges) may define part of or the entiretouch region 16. The connecting surface 24 may define the touch region16 along all or part of the touch surface 12.

The surface acoustic wave generator 14 generates surface acoustic waveshaving a span between by two beam edges that define the touch region 16such that both beam edges are at the sides of the touch region 16. Thebeam edges of the generated surface acoustic waves are at a given leveldown from a peak, such as 3 dB, 6 dB, 10 dB or other level down.Alternatively, the beam edges are where the surface acoustic wave issufficiently above a noise level to provide for reliable (99%) touchsensing. The beam edges define any angular range or radius, such as45-90°. In alternative embodiments, the surface acoustic waves radiateover 180°. Within the range of angles, the surface acoustic waves areabove the noise level. Alternatively, the surface acoustic wavegenerator 14 generates surface acoustic waves along two or more vectors(e.g., edges) with one or more regions in-between with less or littlesurface acoustic wave amplitude. Where multiple surface acoustic wavegenerators 14 are provided, the beam edges of the fan beam of onesurface acoustic wave generator 14 may be within or spaced away from aside edge of the touch region 16.

When more than one surface acoustic wave generator 14 is provided, theregion of overlap or set of all regions covered by surface acousticwaves from one or more surface acoustic wave generator 14 provides thetouch region 16. A combination of one or more surface acoustic wavegenerator 14 and one or more linear transducers with arrays ofreflectors may be used to form the touch region 16 in some embodiments.

In one embodiment, two or four surface acoustic wave generators 14 arepositioned near different corners of a rectangular touch surface 12. Arectangular touch region 16 is formed where touch locations may bedetected due to interference with two or four surface acoustic wavepropagation paths. Reflectors may be provided for reflecting surfaceacoustic waves from the surface acoustic wave generator and/or othertransducers to further diversify the surface acoustic wave detection.

Referring to FIG. 2, the surface acoustic wave generator 14 is providedas a radial transducer 26 adjacent to the touch surface 12 in a specificembodiment. The radial transducer 26 is bonded to the touch surface 12.Other connections may be used, such as clamping. Acoustic wavestransmitted by the surface acoustic wave generator 14 couple to thetouch surface 12 at the boundary surface to generate surface acousticwaves propagating along the touch surface 12. The angle may vary fordifferent radial transducers 26 and touch surface 12 materials.

A fanned-out beam may be used for various layouts in a touchscreensystem. FIG. 1 shows one example layout. The fanned-out beam isgenerated and/or received for a given layout by the transducer 14. FIGS.3-15 relate to various transducers for generation and/or reception ofthe fanned out beam. Following the discussion of the transducers,various layout embodiments are discussed. FIGS. 17-21 and 23 illustratethe various layout embodiments that may use radial transducers.

In the embodiments shown in FIGS. 2-12 and 14, the acoustic wavegenerator 14 includes some form of wedge transducer 26. The wedgetransducer 26 generally includes a wedge 28 (which does not necessarilyhave a wedge shape) and a piezoelectric element 30 connected on a firstsurface of the wedge, and the wedge 28 meets the touch substrate at aboundary surface. Additional components, such as electrical wiring andcurrent or voltage generator, may be provided. Also, a casing or housingmay be provided.

The piezoelectric element 30 is any piezoelectric material. A block ofceramic, composite of posts or ridges in polymer material, or film ofpiezoelectric material may be used. For example, a rectangular block,slab, or plate of piezoelectric ceramic is provided. Electrodes may bepositioned on opposite sides of the piezoelectric material. By changingthe potential across the piezoelectric material, the piezoelectricmaterial mechanically expands and contracts. Varying the electricpotential causes oscillating pressure waves to be generated.

The piezoelectric element 30 typically is flat, such as a plate,allowing efficient contact with a flat surface of the wedge 28. The flator slab shape may provide for more efficient and less costlymanufacturing. The bulk pressure waves generated by the piezoelectricelement 30 are predominantly linear in the sense that power flow isconcentrated in one direction and wavefronts of maximum expansion andcontraction approximate parallel planes perpendicular to the power flowdirection. In alternative embodiments, the piezoelectric element 30 iscurved along at least one surface of the wedge 28. By being curved, thepiezoelectric element 30 generates the pressure waves, at least partly,in a radial pattern.

The wedge 28 may be of varying shape and size, according to variousembodiments. The wedge 28 couples bulk pressure waves induced bypiezoelectric vibrations to surface acoustic waves propagating onsubstrate 10. A well known and used shape for such a coupler is aconventional wedge shape such as shown in FIGS. 16A and 16B. Accordingto some embodiments of the radial transducers, a conventional linearwedge transducer may be used in combination with other elements toprovide the radial propagation of surface acoustic waves. However, forcertain radial transducer embodiments, other shapes that have someportion being tapered in a wedge-like manner may be used and forbrevity, the term “radial wedge” is used to represent such a couplereven in embodiments where the wedge 28 does not have a conventionalwedge shape. Typically, the wedge 28, in transmit mode, is designed todirect bulk acoustic wave energy generated from the piezoelectricelement towards the substrate surface at an angle appropriate forcoherent generation of surface acoustic waves. Any suitable material fortransmitting pressure waves to the touch surface 12 and generatingsurface acoustic waves at the boundary surface between the wedge 28 andthe substrate 10 may be used. In one embodiment, the wedge 28 is asingle piece of polymer such as acrylic or acrylate (e.g. Lucite (PMMA))or any other suitable material transmitting pressure waves at a velocityless than the phase velocity of the desired waves on the substrate.Multiple pieces may be bonded together to form the wedge 28 in otherembodiments. Bonded or multiple piece structures may be used to causereflection or other acoustic wave effects for generating radial surfaceacoustic waves.

The wedge 28 is connected with the piezoelectric element 30. Anyconnection, such as bonding with epoxy, may be used. The bonding agenthas minimal thickness, such as less than ½ wavelength of the pressurewaves. The surface of the wedge 28 mates with and is in acoustic contact(typically via an adhesive bonding layer) with the surface of thepiezoelectric element 30. For example, both are flat or have a samecurvature, at least in a contact region. As combined, the piezoelectricelement 30 may be at any appropriate angle relative to the touch surface12, depending on the configuration of the wedge 28 itself, to couplesurface acoustic waves to or from the touch surface 12.

The pressure waves generated by the piezoelectric element 30 travelthrough the wedge 28 at an angle relative to the touch surface 12.Depending on the speed of propagation of the pressure waves within thewedge 28, the speed of the surface acoustic waves on the touch surface12, and the angle of the pressure waves to the touch surface 12 at theboundary between the wedge 28 and the touch surface 12, surface acousticwaves may be generated. The surface acoustic waves propagate on thetouch surface 12 rather than through the surface 12, and thus propagatein a different direction than the pressure waves when consideringpropagation directions in a cross-sectional plane (such as thecross-sectional plane shown in FIG. 16B). The angles on the touchsurface 12 of propagation are the same as the associated directionalcomponents of the pressure wave vector (i.e., the surface acoustic waveshave the same X and Y vector components or direction, but different Zdirection where Z is into the surface 12 and X and Y are along thesurface 12). That is, in practical engineering terms, the conversionbetween bulk and surface waves does not change the wave propagationdirection in a plan view projection.

According to specific embodiments such as seen in FIGS. 3-8 and 10, theradial wedge 28, having a piezoelectric element connected to a firstsurface of the wedge, may be configured to convert between firstacoustic waves such as bulk pressure waves and second acoustic wavessuch as surface acoustic waves that form a radial pattern on the touchsubstrate. In a transmit mode, the radial transducer causes the surfaceacoustic waves to diverge either initially or after first converging toa focal point under or in front of the wedge 28. The radial wedge 28causes the surface acoustic waves to diverge in the touch region 16 insome embodiments. The configuration is a shape, change in density (e.g.,acoustic impedance), wave guide, or other characteristic causingpressure waves in the wedge 28 to change direction from the linear pathtraveled from the piezoelectric element 30. Reflection, guiding, orother property causes the waves to propagate in a desired direction. Thepressure waves may be made to converge or diverge. For example, thepressure waves converge to a point, line, or area in the radial wedge28. As another example, the pressure waves converge to a point or regionoutside the wedge 28 such that the surface acoustic waves convergetowards the point or region and after converging, the waves diverge. Inthe touch region, the resulting surface acoustic waves diverge.

In one embodiment, the radial wedge 28 is configured to cause thesurface acoustic waves to diverge in the touch region 16 withoutreflection in the touch region 16. The surface acoustic waves generatedat the boundary surface of the wedge 28 and the touch surface 12propagate at angles providing wave path divergence in the touch region16. No reflection or diversion of the surface acoustic waves is neededto provide the radial surface acoustic waves in the touch region 16. Inalternative embodiments, one or more reflectors are provided adjacent tothe wedge 28 for redirecting the surface acoustic waves to the touchregion.

In one example for causing surface acoustic waves to diverge withoutreflection outside the wedge 28, a radial wedge 28 is provided. FIGS.3-8 show examples of radial wedges 28. The radial wedges 28 include areflection surface 40 and a boundary surface (where the wedge and touchsubstrate meet). The reflection surface 40 is convex, concave, or linear(flat). A single continuous reflection surface 40 is provided, butmultiple or discontinuous reflection surfaces may be used. For example,a series of adjacent flat surfaces at different angles form a generallycurved surface.

The reflection surface 40 is an exterior surface of the radial wedge 28.The difference in acoustic impedance of the radial wedge 28 andsurrounding material (e.g., air, plastic, metal or other housingmaterial) causes most of the acoustic energy of the pressure wave toreflect rather than transmit. Alternatively, the reflection surface 40is internal to the wedge 28, such as being a boundary between twomaterials within the wedge with different acoustic impedance.

The reflection surface 40 is positioned relative to the piezoelectricelement 30. The distance away from the piezoelectric element 30,angle(s) of the reflection surface 40, and position of any curve in thereflection surface 40 is set to cause divergence or convergence of thesurface acoustic waves generated at the boundary surface. The pressure,bulk, acoustic or other waves generated by the piezoelectric element 30reflect off of the reflection surface 40, causing surface acoustic waveson the touch surface 12 to diverge. The pressure, bulk, longitudinal orother waves reflected from the reflection surface 40 are in a same mode,but may be in a different mode due to the reflection (e.g., shear wavesgenerated by the reflection). The angle of the pressure waves afterreflection causes generation of the surface acoustic waves in the radialpattern.

FIGS. 3A and 3B show one example embodiment of a radial wedge 28 for aradial transducer 26. The top portion of FIG. 3A is a top view of theradial transducer and the bottom portion of FIG. 3A is a cross-sectionalview of the radial wedge transducer. In this embodiment, thepiezoelectric element 30 is connected to wedge 28 so that the element 30is in a plane 90° relative to the touch surface 12. The reflectionsurface 40 is curved such that the divergence is caused, at least inpart, by the reflection off of the curvature of the reflection surface40. FIG. 3A shows example rays of the direction of wave travel,including before and after reflection from the reflection surface 40.The reflection surface 40 causes the linearly propagating pressure wavesto converge after reflection. After convergence of the pressure waves orresulting surface acoustic waves, the surface acoustic waves diverge.

The angle of the reflection surface 40 causes the pressure waves topropagate back towards the piezoelectric element 30. As shown in FIG.3A, the reflected pressure waves travel between the reflection surface40 and the touch surface 12 or a surface connected with the touchsurface 12. In some embodiments, the pressure waves generate surfaceacoustic waves at the boundary surface prior to passing under thepiezoelectric element 30 (see FIG. 3A). The radial wedge 28 may includea ridge or other portion separating the piezoelectric element 30 fromthe touch surface 12. The angle of incidence of the pressure waves tothe touch surface 12 is set to couple between bulk waves and the surfaceacoustic waves.

FIG. 3B shows an example use of the radial transducer identical to thatshown in FIG. 3A except that it is not bonded to the touch surface 12.The radial wedge 28 is mounted on the bottom surface 22 of substrate 10and positioned with the piezoelectric element 30 mounted closer to atruncated corner of substrate 10 than reflection surface 40. As theradial transducer is on the bottom surface 22, the touch sensor mayenable bezel-less product designs. As discussed above, the reflectionsurface 40 functions as a curved focusing mirror to reflect pressurewaves propagating in the wedge material. The generated surface acousticwaves propagate from the wedge 28 towards a rounded connecting surface24 of the substrate 10. The rounded connecting surface 24 transfers thewave between substrate surfaces resulting in surface acoustic wavespropagating over the touch region 16 (surface acoustic waves are shownin dotted line arrows to indicate the propagation on top surface 20opposite to bottom surface 22 where the radial transducer is mounted).The bezel-less product compatible surface acoustic wave touch sensorsare described in more detail in U.S. patent application publication no.2011/0234545, which is incorporated by reference. In alternativeembodiments, the radial transducer 26 shown in FIG. 3B is turned 180°and is mounted on top surface 20 so that the surface acoustic wavespropagate over the touch region 16 without traversing the connectingsurface 24 (and a bezel may cover the transducer).

FIG. 4 shows another embodiment of a radial wedge 28 similar to theembodiment shown in FIG. 3 except having a longer and less steeplyangled reflection surface 40. The top portion of FIG. 4 shows simplifiedtop views of the radial transducer, and the bottom portion of FIG. 4shows a cross-sectional view of the radial transducer. In thisembodiment, the piezoelectric element 30 is connected to wedge 28 sothat the element 30 is in a plane 90° relative to the touch surface 12.The reflection surface 40 is angled to cause the pressure waves toreflect while continuing to propagate away from the piezoelectricelement 30. The angle is set to cause the pressure waves incident on theboundary with the touch substrate 10 to generate surface acoustic waves.In one example using an acrylic wedge 28 and glass touch surface, theangle of the pressure wave direction to the reflection surface is about16.5°, causing an angle of incidence at the boundary to the touchsurface of about 33°. Depending on materials used, orientation ofpiezoelectric element 30, and other design choices, the optimal anglesmay vary.

The curvature of the reflection surface 40 causes the reflected pressurewaves to converge. After convergence in the wedge 28 of the pressurewaves and/or convergence on the touch surface 12 of the surface acousticwaves, the surface acoustic waves diverge.

With the top portion showing a top view of the radial transducer and thebottom portion showing a cross-sectional view of the radial transducer,FIG. 5 shows another example radial wedge 28. The reflection surface 40causes reflection in a diverging pattern rather than initial convergenceshown in the embodiment of FIG. 4. The reflection surface 40 shown inFIGS. 3 and 4 provides a convex wedge shape and results in convergingbeams, while reflection surface 40 of the embodiment of FIG. 5 providesthe wedge with a concave and diverging reflection surface 40. In thisembodiment, the piezoelectric element 30 is connected to wedge 28 sothat the element 30 is in a plane 90° relative to the touch surface 12.

FIG. 6 is another embodiment of a radial wedge 28. The top portion ofFIG. 6 shows a top view of the radial transducer and the bottom portionof FIG. 6 shows cross-sectional views of the radial wedge transducer.The reflection surface 40 is the upper surface of the radial wedge 28rather than a side surface (as with FIGS. 3-5). The piezoelectricelement 30 is at an angle other than 90° to the touch surface 12, suchas angled to generate pressure waves propagating towards a top of thewedge 28 and away from the touch surface 12. The reflection surface 40is curved to cause convergence of the reflected pressure waves, butcurvature for initial divergence may be used. The reflection surface 40may be curved along multiple dimensions to cause the reflected pressurewaves to intersect the boundary at the desire angle.

FIG. 7 shows an embodiment with multiple reflection surfaces 40. The topportion of FIG. 7 is a top view of the radial transducer and the bottomportion of FIG. 7 is a cross-sectional view of the radial wedgetransducer. The pressure waves reflect once to converge. Pressure wavesfrom the right half reflect towards the left half and vice versa. Thereflection surfaces 40 may be flat or curved to distribute the energy ofthe waves as desired. In other embodiments, only one reflection surface40 is provided such that the piezoelectric element 30 is at an angleother than 90° to the center of the radial pattern of the surfaceacoustic waves.

The piezoelectric element 30 is positioned with the wedge 28 to causethe pressure waves as originally generated to be at the intended anglefor causing radial surface acoustic waves. The reflection surfaces 40change the convergence or divergence in two dimensions without changingthe angle of incidence along another dimension. Alternatively, thereflection surfaces 40 change the angle to generate surface acousticwaves.

FIG. 8 is another embodiment with the piezoelectric element 30 angled togenerate pressure waves for generation of surface acoustic waves. Thetop portion of FIG. 8 is a top view of the radial transducer, and thebottom portion of FIG. 8 is a cross-sectional view of the radial wedgetransducer. The reflection surface 40, which has a generally curved orparabolic shaped, is positioned to reflect the center pressure wavesoutward rather than reflecting the pressure waves at the edge of theradial wedge outward or inward.

Other shapes for the radial wedge 28 may be used. Combinations of thefeatures of the examples in FIGS. 3-8 may be used. In one alternativeembodiment, some or all of the pressure waves are reflected multipletimes. To design the exact shapes of the radial wedges 28 for radialtransducers, use is made of: 1) the reflection law that the angle ofreflection equals the angle of incidence (assuming no mode conversion),2) in plan view projection, no change in wave propagation direction whenthe pressure wave in the wedge material refracts and mode converts intoa surface acoustic wave in the substrate and 3) Snell's law that thesine of the refracted angle divided by the transmitted wave phasevelocity equals the sine of the incident angle divided by incident wavephase velocity. The correct shape in a ray tracing approximation of thereflection surface 40 may be verified by determining that at each pointon the surface, the surface normal, incident ray and reflected ray arecoplanar and the angle between the surface normal and incident rayequals the angle between the surface normal and the reflected ray. Whenthe reflected pressure wave refracts and mode converts to a surface wavein the substrate, the refracted ray maintains the same direction of thereflected ray in plan view, and for a correct design lead to the desireddiverging surface acoustic waves (perhaps after first converging at afocal point). Optimal refraction between pressure waves in the shapedwedge and surface acoustic waves in the substrate may be verified bydetermining that in the vertical plane containing the reflected andrefracted rays that the angle (90°−θ) between pressure wave rays and thesubstrate normal meets the Snell's Law condition thatsin(90°−θ)/V_(p)=)sin(90°/V_(saw) or cos(θ)=V_(p)/V_(saw), where V_(p)is the pressure wave phase velocity in the wedge material and V_(saw) isthe surface acoustic wave phase velocity. While more systematic designmethods may be used, candidate designs may be iteratively developeduntil the above conditions are met (i.e., experimentation may be used).It may be desirable to go beyond the ray tracing approximation to a fullwave mechanics studies either experimentally or via simulation. The sameprinciples may be applied if the piezoelectric element 30 is a shearmode rather than standard pressure mode, except that rays within theshaped wedge material correspond to shear waves with bulk shear wavephase velocity rather than pressure waves. It is also possible to designradial wedge transducers in which conversion between shear and pressurewaves occur at the reflection surface 40, in which case a reflectionversion of Snell's law rather thanangle-of-reflectance-equals-angle-of-incidence applies to thereflection. For example, the ray from the piezoelectric element 30 tothe reflection surface may correspond to a pressure wave, and the rayfrom the reflection surface to the substrate may correspond to a shearwave.

FIG. 9 shows another embodiment of a radial wedge transducer 26 shown incross-section. Like a conventional linear wedge transducer such as shownin FIG. 16, the wedge 28 and piezoelectric element 30 have flatsurfaces. Curved surfaces may be provided in other embodiments. Allsurfaces except the boundary surface 44 of the wedge 28 to the touchsurface 12 may be flat with a tolerance smaller than one or ½ awavelength of the pressure waves. Alternatively, one or more surfacesare curved or textured. For example, injection-molding gating bumps maybe on one or more surfaces. Tighter tolerances may be used to assist inbonding with a very thin adhesive layer. The piezoelectric element 30and wedge 28 have a standard shape or shape for generating surfaceacoustic waves at the boundary 44 in a linear pattern. Reflection isavoided, such as by generating pressure waves predominantly directed atthe boundary.

Unlike the conventional linear wedge transducer where the boundarysurface 44 is flat, to generate the surface acoustic waves in a radialpattern, the boundary surface 44 of the radial transducer according tothis embodiment includes an interference structure where selected raysare blocked or phase shifted. The interference structure is formed fromslots, different material, apertures or other structure for interferingwith the propagation via absorption, reflection or phase shifting. Thestructure is on the boundary surface 44, but may be away from theboundary surface within the volume of the wedge 28 so that the intensityor phase of pressure waves reaching the boundary surface 44 aremodulated as desired. The structure is a series of parallel stripes atleast where the pressure waves are incident on the boundary surface 44.In alternative embodiments, curved slots or interference structurehaving any shape or pattern (e.g., a plurality of hemispheres) isprovided.

In one embodiment, the interference structure is made up of slots milledfrom the boundary surface 44 of the wedge 28, as shown in the leftportions of FIG. 9. Other treatments may be used. For example, the slotsmay be formed by molding. Texturing, surface treatment, differences indensity, or other characteristics may be used to form the interferencestructure. Alternatively, the interference structure may also beprovided on the substrate surface rather than the wedge itself, such asby etching and machining grooves or slots in the glass surface.

The interference structure absorbs, reflects, phase shifts and/orotherwise disrupts pressure waves. The disruption causes the surfaceacoustic waves to diverge (perhaps after converging). For example, FIG.9 shows a slot pattern on the boundary surface 44. Symmetric slots withdifferent widths are provided (left portion of FIG. 9). The un-milledzones couple to the transmitted surface acoustic wave, and the milledzones do not couple. The surface acoustic waves being generated throughor after the interference structure radiate or propagate in a radialpattern (e.g., fan beam). The spacing and shape of the interferencestructure provides a fan beam with a desired energy distribution acrossthe different angles.

In one embodiment, a material with a different density is placed in theslots or forms the interference structure. Rather than blocking, theinterference structure allows for transmission but at a different speedof propagation. By choosing the depth and density of the interferencestructure, a phase shift may be introduced. A phase shift of 180° is ofparticular interest. By choosing material with different attenuation, anapodization may be introduced. The phase shift and/or amplitudeweighting of different parts of the aperture may defocus or causedivergence. For example, the phase shift reduces a forward beamamplitude, providing for more even distribution of acoustic energy overthe fan beam. The transducer design of FIG. 9 (left portion) usessimilar wave mechanic principles also used for holograms in optics. Inone way to design the pattern in FIG. 9, focal points are chosen infront of the transducer, the distance from each point on the front ofthe wedge to the desired focal point is computed in units of surfaceacoustic wave wavelengths, and those points which are within a quarterwavelength of being an integer number of wavelengths from the desiredfocal point are identified. Via Huygen's principle, waves propagatingfrom these points constructively interfere, if not in perfect coherentphase, so as to contribute to wave amplitude at the desired focal pointwhile waves propagating from the remaining points, had they not beenremoved, would have destructively interfered with the wave amplitude atthe desired focal point. By removing destructively interfering rays viaan interference structure, a coherent focus at the desired focal pointremains. By phase shifting the rays through the remaining points by180°, rather than eliminating them, all points along the front of thewedge contribute to a coherent focus. The focal regions are selected toprovide a fan pattern.

In yet another embodiments, the pattern of decoupling or 180° phaseshift shown to the left of FIG. 9 may be implemented not at a boundarysurface 44, but rather at the boundary between piezoelectric element 30and wedge 28 or within the piezoelectric element 30 itself. For example,the surface facing piezoelectric element 30 of wedge 28 may be providedwith a pattern of slots leading to focusing pressure wave front in thewedge 28 that converts at boundary 44 into a focusing pattern of surfaceacoustic waves propagating in the substrate. Alternatively, the patternshown to the left of FIG. 9 may be re-interpreted as an electrodepattern on piezoelectric element 30 where the darker shaded regionscorrespond to electrodes driven (or received) 180° out of phase withrespect to the electrodes corresponding to the lighter shaded regions.If electronics support additional shifts of the excitation signal,further embodiments are possible, such as an electrode pattern withthree types of regions of relative phases of 0°, 120° and 240° to moreefficiently excite (or receive) a focusing pressure wave propagating inthe wedge 28

FIG. 10 shows another embodiment of a radial wedge transducer 26 formedwith a radial wedge 28. The piezoelectric element 30 is curved. Thepiezoelectric element 30 and wedge 28 are formed as if a section wererotated about a vertical axis of rotation, providing a conical shape.FIG. 10 shows a 90° rotation, but greater or less rotation may be used.The curve is provided by a smooth variation or by connecting togetherflat slabs at slight angles to each other. The piezoelectric element 30may be formed on the radial wedge 28 or formed separately and bonded tothe radial wedge 28. The piezoelectric element may be formed as a curvedpiece by cutting from a piezoelectric cone element with radial(thickness) resonance at about 5.53 MHz or other desired frequency.About accounts for manufacturing tolerances. Alternatively, a flexiblesheet piezoelectric material, such as PVDF, is deposited or cut to theappropriate shape. The piezoelectric element 30 is poled in the radialdirection.

The curve causes the pressure waves to radiate in a fan beam or radialpattern. A uniform radial surface acoustic wave pattern corresponding tothe angle of rotation of the piezoelectric element is generated.

In the embodiment shown in FIG. 10, the piezoelectric element 30 isangled to transmit pressure waves to the boundary surface withoutreflection. In other embodiments, the curved piezoelectric element 30 ispositioned to reflect the pressure waves off of a surface 40 of thewedge 28, such as the arrangements shown in FIG. 3A and FIG. 4. Thereflecting surface 40 has a similar or different amount of rotation orcurvature for controlling the divergence of the surface acoustic waves.Such a hybrid of the designs of FIG. 3A or FIG. 4 and FIG. 10 may allowuse of a curved piezoelectric element 30 that is a section of a cylinderrather than a section of a cone. Piezoelectric material in the shape ofhollow cylinders are typically cheaper and more readily commerciallyavailable than sections cut from cones.

FIG. 11 shows another embodiment of a surface acoustic wave generator14. With this embodiment of surface acoustic wave generator 14, aconventional wedge 28 and piezoelectric element 30 generate surfaceacoustic waves propagating generally or predominantly in a lineardirection. Alternatively, a grating transducer or other surface acousticwave generator is used.

A curved reflector 60 causes the surface acoustic waves to reflect andthus diverge. The curved reflector 60 is a surface acoustic wave mirror,such as an etched channel in the touch surface 12, reflection grating,or a glass surface edge 24. Other reflectors may be used. The curvatureis shaped to radiate the surface acoustic waves in the desired fan beam.The curvature is continuous, but may vary to provide greater amplitudeat one or more angles in the radiation pattern. In alternativeembodiments, the curved reflector 60 is formed from a plurality oflinear reflectors at different angles.

The curved reflector 60 is adjacent to the wedge 28 of the wedgetransducer 26. The curved reflector 60 may contact or have a portionagainst part of the wedge 28. As shown, the curved reflector 60 isentirely spaced from the wedge 28. Even spaced from the wedge 28, thecurved reflector 60 is adjacent to the wedge 28 relative to the touchregion 16. For transmission, the surface acoustic waves reflect from thecurved reflector 60 and then propagate into the touch region 16. Thecurved reflector 60 may alternatively be, at least in part, within thetouch region 16.

In another embodiment of a surface acoustic wave generator 14, thesurface edge 24 of the touch surface 12 is used to reflect or transmitthe surface acoustic waves. By being curved or having parts at differentangles, the surface edge 24 causes the surface acoustic waves topropagate in the radial pattern.

In the example shown in FIG. 12, the wedge 28 and piezoelectric element30 or other surface acoustic wave generator 14 is on the bottom surface22 of substrate 10. FIG. 12 shows two opposite surfaces, the bottomsurface 22 and the top surface 20 unfolded in order to illustrate thewave paths from bottom surface 22 via connecting surface 24 to topsurface 20. The upper right side of FIG. 12 shows the bottom surface 22,and the lower left side of FIG. 12 shows the top surface 20. The wedgetransducer 26 may transmit the surface acoustic waves linearly towardsthe connecting surface 24 at a corner, or alternatively wedge transducer26 may be replaced with a radial transducer that by itself partiallyprovides the desired fan out of radial beams. The connecting surface 24at the corner is rounded in both side and plan view, allowing thesurface acoustic waves to propagate over or around the connectingsurface 24 onto the top surface 20 of the touch substrate 10. Inaddition to being rounded from the back 22 to the front 20, theconnecting surface 24 is curved within the plane of the top 20 or bottom22. The curve of the connecting surface changes the angle of the wavepropagation. The waves at different locations along the connectingsurface 24 are angled to converge. The convergence occurs on theconnecting surface 24 or on the top surface 20 adjacent to theconnecting surface 24. After convergence, the surface acoustic wavesdiverge in the touch region 16. Alternatively or in addition, the curvedcorner of the substrate causes the surface acoustic waves to diverge.Convex or concave corners may be used.

This example may be used on a touch surface 12 to be used in azero-bezel touch monitor or product. The curve of the connecting surface24 causes the divergence to occur immediately adjacent to or on theconnecting surface 24. Alternatively, the curve of the connectingsurface 24 is opposite, causing the surface acoustic waves to divergealong the connecting surface 24. As a result, almost the entire or theentire top surface 20 of the touch substrate 10 may be used for touchsensing.

FIG. 13 shows another embodiment of a radial acoustic wave generator 14using curved surface feature pattern 64 over the touch substrate 10.According to a specific embodiment, a grating pattern 64 generally beingcurved shapes (or perturbation elements) formed on the top surface 20 ofthe touch substrate 10 generates surface acoustic waves when apiezoelectric element on a bottom surface 22 of the touch substrategenerates bulk pressure waves from bottom surface 22 toward gratingpattern 64. The grating pattern 64 causes surface acoustic waves toradiate in a fan beam or radial pattern rather than along a line on thetouch region of substrate 10. According to the illustrated embodiment,each of the plurality of curved perturbation elements is generallyconcentric to the others and the pattern 64 has a square shaped outline.However, other shaped outlines of the pattern may be used in variousembodiments. The grating pattern has a short curved element 64 ₁ closestto the corner of the substrate 10 (or furthest from the touch region),followed by progressively longer curved elements (up to the longestcurved element 64 _(n)) that are progressively closer to the touchregion, in order to provide the divergent radial wave pattern on thetouch region of top surface 20 of the substrate. In some embodiments,the shape of the grating pattern 64 may be different than a square (forexample, the elements may have a fan outline shape such as shown in FIG.23). In other embodiments, the short curved element 64 ₁ is farthestfrom the corner of the substrate 10. Other combinations of short andlonger curved elements 64 may be used. In some embodiments, the gratingpattern 64 is etched, printed, or deposited on a top surface 20 of thetouch substrate 10. Any number of perturbation elements may be used.

The piezoelectric element 30 is on an opposite surface (bottom surface22) of the touch substrate 10 than the grating pattern 64. Thepiezoelectric element 30 may be generally parallel with the top surface20, but may be at an angle. The pressure waves are directed at thegrating through the bulk of the substrate. The pressure waves generatedby the piezoelectric element 30 cause the curved grating to generate thesurface acoustic waves in the diverging radial pattern.

In another embodiment, a comb transducer in the general form of thepattern 64 may be provided. Instead of being on a bottom surface 22, thepiezoelectric element 30 is against or on top of the curved gratingpattern 64 that is formed on the top surface 20 of substrate 10.Pressure waves generated by the piezoelectric element 30 cause thecurved pattern 64 to generate the surface acoustic waves in thedivergent radial pattern.

In yet another embodiment of the pattern 64, an interdigital transducermay be provided, where the pattern 64 is of interspersed electrodes thatare curved or arranged to cause a radial fan beam. Every even element inthe pattern is connected together to a first conductor, and every oddelement in the pattern is connected together to a second conductor whichis charged oppositely to the first conductor, so that the elements inpattern 64 form interdigitated electrodes formed over the touchsubstrate. The pattern 64 is thus on or deposited on a piezoelectricfilm, such as polyvinylidene fluoride (PVDF), that is positioned on thetouch surface. The angular span of the fan or radial pattern of surfaceacoustic waves may be, for example in the range of 45° to 90° or perhapseven larger including 180°. In response to changes in potential betweenthe curved electrodes 64 of the interdigital transducer, thepiezoelectric film generates surface acoustic waves in the radialpattern radiate over a span of angles, such as over 45°.

FIG. 14 shows another embodiment of a surface acoustic wave generator14. The transducer may include a conventional wedge transducer 26 or agrating transducer. The transducer generates the waves to propagatealong a line (using a conventional linear wedge) where the surfaceacoustic waves propagate predominantly in a linear pattern on the touchsurface 12.

To fan out the surface acoustic waves, one or more acoustic lenses 70are provided. The lens may be formed by printing material on the glasssurface, such as printing glass-frit or other material that modifies thesurface acoustic wave phase velocity. The lens 70 may be etched into,printed on as an ink, or bonded onto the touch surface 12 adjacent tothe transducer 26. As previously discussed in connection with FIG. 12,in one embodiment, the lens 70 is formed as a curved corner connectingsurface 24. The corner connecting surface 24 of the glass of the touchsurface 12 may be shaped and used to redirect the surface acoustic wavesin order to obtain a radial wave pattern on the touch surface.

The lens 70 has a focus causing the incident surface acoustic waves todiverge over a range of angles directed towards a touch region 16 of thetouch surface 12. A wide range of angles may be provided, according tovarious embodiments. If lens 70 is fabricated by simply adding to thearray mask a region of printed material in an appropriate lens, therelatively modest change in surface acoustic wave phase velocity, suchas a few percent, may support only a limited range of angles. This rangeof angular spread may be increased by including additional lenses likelens 70. Alternatively the design and manufacturing processes tofabricate lens 70 may be selected to provide a more dramatic change,such as a factor of two, of surface acoustic wave velocity within lens70. The lens 70 and the transducer 26 are positioned on a same side ofthe touch substrate 10. The lens 70 causes the surface acoustic waves todiverge as the waves travel over the touch substrate 10 in the touchregion 16. The divergence is provided without reflection of at least thesurface acoustic waves used for touch sensing.

FIG. 15 shows a method for generating radial surface acoustic waves. Themethod uses one or more of the surface acoustic wave generators 14discussed above or a different type of surface acoustic wave generator14. The method is implemented in the order shown, but a different ordermay be provided. For example, act 82 occurs simultaneously with act 80using a curved piezoelectric. As another example, act 84 occurs prior toact 82, such as using the surface acoustic wave generator 14 of FIG. 12.Additional, different, or fewer acts may be provided.

In act 80, acoustic waves are generated. The acoustic waves are pressurewaves. Alternatively, the acoustic waves may be shear or other wavetypes. The waves are generated by a piezoelectric or other diaphragm.For example, a microelectromechanical membrane generates pressure waves.

In act 82, the waves are radiated in a radial pattern. The generatedwaves are reflected, focused, diverted, or otherwise caused to diverge.Any amount of divergence may be provided, such as at least 45°. Anydistribution of energy over the range of the fan beam may be used, suchas generally even distribution. The pressure waves and/or the surfaceacoustic waves diverge. The divergence may occur without convergence oroccur in response to convergence of waves.

In act 84, the pressure waves generate surface acoustic waves. A modalconversion causes the surface acoustic waves in response to pressurewaves incident on the touch surface. On the touch substrate, thegenerated surface acoustic waves diverge.

Instead of being designed to produce a broadly fanned out beam, thesurface acoustic wave generators may be designed with a very long focallength. While very long focal length radial transducers provideinsufficient angular spread of radial beams to be of value in the touchsensor layout designs supporting multiple touch functionality, such aswill be discussed below, very long focal length radial transducers mayprovide an incremental improvement in the design of conventional SAWtouchscreens. The focal length is about half the length of a reflectivearray, but may be tuned longer or shorter to optimize SAW touchscreensignal quality. The beam from such a long-focal length transducer isinitially converging and may reduce the fraction of beam power thatspreads beyond the footprint of the reflective array. Such misdirectedacoustic power is not only lost signal but also a potential source ofundesired acoustic parasites. In this fashion, very long focal lengthradial transducers may be of value to increase signal and reducebackgrounds even for otherwise conventional SAW touchscreen designs.

FIG. 1 shows an example layout for a touch sensor using a radial patternof surface acoustic waves for illustration purposes. The radialtransducer 14 generates the radial pattern of surface acoustic wavesrepresented by the rays 18. The radial pattern is in the touch region16. FIG. 1 shows the radial pattern of waves diverging as they aretransmitted from radial transducer 14 across the touch region 16. In thereverse direction, assuming the direction of the rays (arrows) isopposite that shown in FIG. 1, the radial transducer 14 would receivethe radial pattern of waves that would converge toward transducer 14.

The touch sensor layouts described herein are for a touch sensor or atouchscreen. A touch sensor uses an opaque, semi-transparent, ortransparent substrate regardless of whether a display is provided behindthe sensor. A touchscreen is a touch sensor with sufficientlytransparent touch substrate to be provided above a display. Displaysbeing typically rectangular, touchscreens also are rectangular but anyshape may be used.

FIG. 1 is an example of directly generating the radial pattern. Inalternative embodiments, the radial propagation pattern is generated byreflection, such as using a conventional wedge or other transducertransmitting acoustic energy along a linear propagation direction andthen reflecting the acoustic energy in a diverging radial patterndifferent from the linear propagation direction such as seen in FIG. 11.In still other alternative embodiments, such as shown in FIG. 14, theradial propagation pattern is generated with refraction by using aconventional wedge or other transducer with one or more lenses to causethe linear propagation of waves incident on the lens to then diverge.

FIGS. 17-21 show alternative embodiments of touch sensor layouts using aradial pattern of acoustic waves. The radial pattern is of a fan beamwith generally uniform amplitude across the width of the beam.“Generally” accounts for variation but still with an amplitude above anoise level, allowing detection of touch. For example, the amplitude ofthe signal corresponding to at any given touch location is within 6 or10 dB of a peak amplitude. The beam edges fall below this level. In thefigures, this radial pattern is represented by rays for simplification.Alternatively, the radial pattern is of two or more distinct beamsrepresented by the rays such as would be produced if the smoothly curvedreflective surface 40 of in a radial wedge transducer design of FIG. 3Awere replaced by a faceted geometry composed of flat reflectivesurfaces. A continuous swath of beams may be desired in order to enablemeasurement of a continuous coordinate. Nevertheless for applicationsfor which only discrete coordinate values are needed, it is an option touse distinct beams that propagate in a diverging or converging patternacross the touch region. The rays may correspond to acoustic paths alongwhich a touch may be detected. Where reflective arrays are used, due tospacing of any reflective elements, discrete acoustic paths may bedefined for detection. A further simplification is provided in FIGS.18-21 where only the rays representing acoustic wave paths intersectedby a touch are shown.

FIG. 17 shows a radial transducer 91 for generating surface acousticwaves on the touch surface 12. Any of the radial transducers 91discussed above may be used, such as a radial wedge transducer or acurved grating. The radial transducer 91 is on or bonded to thesubstrate. The radial transducer 91 generates the acoustic energy alongdifferent radial lines 18, either as a fan beam or discrete beams.Alternatively, a transducer generates acoustic energy propagating alonga line and one or more reflectors or lenses cause the acoustic energy tofan radially (for example, as seen in FIG. 11 or 14).

A receive transducer 96 is positioned to receive acoustic waves. Thereceive transducer 96 is any type of conventional transducer, such as alinear wedge or grating transducer. In the embodiment shown, the receivetransducer 96 receives acoustic energy from substantially (accountingfor beam width or variance) one direction represented by the arrowdirected toward transducer 96. As seen in FIG. 17, surface acousticwaves are transmitted radially from radial transducer 91 across thetouch surface 12 toward a reflective array 92 having spaced apartreflective elements 94, each reflective element in the array beingdifferently angled from the others in order to reflect the radialsurface acoustic waves into a linear direction toward receivingtransducer 96, as described further below. As shown in a simplifiedmanner, the array 92 of reflective elements 94 reflects the acousticenergy from transducer 91 in the radial pattern to a line directed atthe receive transducer 96. In alternative embodiments, the reflectors 94are positioned to reflect the acoustic energy in a radial pattern, suchas reflecting in a converging pattern to the receive transducer 96.Since the acoustic energy is received from more than one direction, thereceive transducer 96 may be a radial transducer. In yet otherembodiments, the transducer 96 is used to transmit the acoustic energyin a linear direction across the reflective array 92, which partiallyreflects the linearly propagating waves into a converging radial patterntowards the radial transducer 91 acting as the receive transducer (thisis illustrated merely by reversing the direction of the arrows of thepropagation rays in FIG. 17).

The receive transducer 96 is positioned relative to the reflectiveelements 94 and/or the transmit radial transducer 91 to receive theacoustic energy from the different radial lines 18. In one embodiment,there is a sufficient density of reflective elements 94 (most of whichare not shown) so that each radial line 18 intersects multiplereflective elements 94. The set of acoustic paths corresponding toradial lines 18 produces a continuous swath or fan of beams. Inapplications where it is desired to measure discrete angular coordinatevalues rather than measure continuous touch position coordinates, array92 may be formed of discrete clusters of reflective elements 94corresponding to angles or radial lines 18 along which acoustic energyis received. The reflective elements 94 may be spaced (e.g., center tocenter) to optimize coherent scattering for the desired change indirection from that of the incident radial beam to that of a beamdirected towards transducer 96. This may result in a variable spacing ofreflector elements 94 that deviates from integral multiples ofwavelength.

Reflective elements 94, which may be glass frit printed or patterned toreflect at least some of any incident acoustic energy, are sized andshaped to reflect acoustic energy that has traveled across or is goingtowards the touch region 16. The reflective elements 94 are positionedto redirect at least some of the surface acoustic waves from the radialpattern to propagate towards another reflector and/or the receivetransducer 96. The angle of each reflective element 94 is set based onthe angle of the incident acoustic path and the location to which theacoustic energy is to be reflected. For parallel acoustic paths derivedfrom 90° scattering, the reflective elements in a conventionalreflective array are uniformly at 45°. However, for radial acousticpaths, the reflective elements 94 are oriented to support reflectionswhere the angle of incidence equals the angle of reflectance, and suchan array 92 of reflective elements 94 may be referred to as a “radialreflective array”. The reflective elements 94 thus may be at variousangles besides 45°. For example, to satisfy the angle of incidenceequals angle of reflectance, the angle between the axis of reflectorarray 92 and individual reflectors 94 may vary as (90°−φ/2) where φ isthe radial beam angle for the beam indicated in FIG. 17. With the radialreflective array's elements 94 in the line as shown in FIG. 17 and theacoustic paths radiating from transducer 91 at different angles, eachreflective element 94 has a different angle to reflect the incidentradial acoustic energy in a linear direction to the receive transducer96.

While five reflective elements 94 are shown for simplicity in FIG. 17,many more may be provided. For example, the element 94 are spaced, in arange from less than one to more than a few wavelengths apart along theline forming the array 92. For interacting with parallel acoustic pathsand reflection by 45°, the reflective elements 94 may be spaced alongthe array axis at integral numbers of acoustic wave wavelengths. For theradial pattern, the spacing may be non-uniform. The reflective elements94 are spaced to provide phase coherence between sequential elements 94.For example, to provide phase coherence, the spacing “S” betweenadjacent reflective elements 94 may be according the formulaS=nλ/(1+cos(φ)) where n is an integer, λ is the surface acoustic wavewavelength and φ is the angle between radial beam angle and the axis ofreflector array 92. Due to attenuation of the surface acoustic wave asit propagates in the substrate and shadowing due to reflective elements94 between the scattering point and transducer 96, signals correspondingto longer acoustic paths tend to be weaker than signals corresponding toshorter acoustic paths, thus leading to a need for signal equalizationmethods. One such method is to use n=1 for the longest acoustic pathsand larger values of n for shorter acoustic paths. Another such methodis to design the radial transducer 91 so that the amplitude to emittedradial surface acoustic wave beams vary with radial beam direction angleφ so as to be stronger for longer acoustic paths and weaker for shorteracoustic paths. The reflective elements 94 of the array 92 are shownalong a line, but in other embodiments the elements 94 may be arrangedalong a curve or other non-linear shape, or with a complex or simpledistribution.

Due to the different path distances, the acoustic energy along differentradial paths is received at different times by the receive transducer96. The different timing may be used to identify one or more radialpaths 18 along which acoustic energy is attenuated. If a touch(represented by 90) intercepts an acoustic path, the touch 90 attenuatesthe received signal at a delay time corresponding to the angle φ of theintercepted radial beam. A polar coordinate detection is made. Using theradial pattern alone, the angle of the touch 90 may be detected. Todetect a point location of the touch 90, additional acoustic paths ordirections of travel may be used.

Due to the use of a radial transducer, reflectors, waveguides, and/orother structure, at least part of the radial wave pattern is provided inthe touch region 16 between the transmit transducer 91 and receivetransducer 96. One or more portions of the acoustic paths may not be inthe radial pattern. All or only part of the touch region 16 uses theradial pattern for touch sensing. Other patterns of the same ordifferent acoustic paths may cover other parts of the touch region. Theacoustic paths along which detection is performed are spacedsufficiently close such that a stylus, finger, and/or finger nail may bedetected. Greater resolution may or may not be provided for covering thetouch region, according to different embodiments.

The radial pattern diverges (or converges) over an angular span or arcΔφ. The beam edges are over a 20°, 45°, 90°, 180° or other arc. The arcmay be greater or lesser. The arc is within the touch region 16. Whileshown as an evenly distributed or simple divergence, the radial patternmay include non-linear paths. For example, reflections or otherdisturbances may cause or be used to cause acoustic energy along some, asubset, one, or all of the acoustic paths to change direction within thetouch region 16.

FIG. 18 shows an example using multiple radial patterns, resulting inintersecting directions of travel of acoustic waves, where the touchsurface, substrate, and corresponding touch region are triangular. Thetriangular touch sensor is formed from three groups of a transmittransducer 91, a receive transducer 96 and an array 92 of reflectors 94.For an equilateral triangle touch surface, the arc for each radialpattern is about 60°. Non-equal arcs may be used. Due to the differentgeometric arrangement, the angle and spacing of the reflectors 94 (notshown for simplicity) may be different than provided for the arrangementof FIG. 17.

A pair of touches (white circles in the touch region) is illustrated.There is no dual touch ambiguity as the point location of each touch maybe determined. Each receive transducer determines an angle for eachtouch, so three angles are provided for each touch. Two angles may beused to determine the location of one touch. The other angle may be usedto resolve the ambiguity for simultaneous touches. Only the two truetouch positions are consistent with a measured angle from an attenuatedradial beam from each of the three radial transducers 91. Thisarrangement allows for multi-touch applications involving two or moresimultaneous touches. Intersections of triples of attenuated radialbeams uniquely locate each touch.

FIG. 19 shows a touch sensor using a radial pattern on a rectangulartouch region or substrate. The touch sensor of FIG. 19 may also resolveambiguity for multiple, simultaneous touches using a layout thatincludes one radial transducer subsystem in addition to standardAdler-type X and Y measuring arrays and transducers (e.g., parallel wavepatterns).

For the parallel wave patterns, two sets of transmit transducers 100,transmit reflective arrays 102, receive reflective arrays 104, andreceive transducers 106 are provided. It is understood that the transmitand receive directions may be reversed in some embodiments. Conventionalpairs of arrays 102, 104 of reflective elements create a set acousticpaths between the transmit transducer 100 and the receive transducer106. The two sets are perpendicular to each other, such as correspondingto an X axis and a Y axis. Four acoustic paths are shown in FIG. 19 forthe two touches (white circles), two horizontal and two vertical. Otherpaths exist, but are not shown to avoid clutter. The paths are parallelto each other for a given direction (i.e., two sets of parallel acousticpaths).

The two parallel wave patterns covering the entire touch region alongtwo directions are sufficient to determine a single touch location at agiven time. If simultaneous touches occur, there are two paths withattenuation in the X direction and two in the Y direction. The detectionis not sufficient to resolve the ambiguity between the four possiblelocations (dashed and full circles). One or more radial patterns thusare provided to resolve the ambiguity.

Any radial pattern may be used, such as providing for two or moredifferent radial patterns to cover different parts of the touch region.In the embodiment shown in FIG. 19, a single radial pattern is used. Tocover the entire touch region, the radial pattern has an about 90° arc.As a result, the acoustic energy of the radial pattern is transmittedtowards or away from two peripheral edges of the touch region. Radialreflective arrays 92 are provided along the two edges. There is morethan one option for reflective element orientations, so radialreflective arrays 92 in FIG. 19 are shown schematically as gray areaswithout the reflective elements being explicitly shown. The reflectorscould be angled to reflect the acoustic energy to one transducer 96 insome embodiments, but then there may be ambiguity due to similar orequal path lengths from waves traveling to each of the substrate edges.In a specific embodiment, the radial reflective arrays 92 may merge at acorner and be positioned to reflect the acoustic energy to differentreceive transducers 96 as shown in FIG. 19, where a separate receivetransducer 96 is provided for each edge. One receive transducer 96detects perturbations of the radial beams above the diagonal of thetouch area, and another receive transducer 96 detects perturbations forradial beams below the diagonal. The receive transducers 96 are spacedapart such as shown, or may be positioned adjacent each other in acorner common to the two edges (i.e., the corner opposite the radialtransducer 91).

The radial reflective arrays 92 are positioned in front of (as shown) orbehind the conventional arrays 102, 104. The reflective elements 94 ofthe arrays 92 allow sufficient acoustic energy to pass that detection isprovided despite the waves passing through the array 92. An individualreflective element 94 may reflect on the order of 1% of incident surfaceacoustic wave energy and transmit the remainder. A significant fractionof the surface acoustic wave energy incident on arrays 92 propagatesthrough arrays 92 to arrays 104.

As shown, the arrays 92 scatter radial beams directly towards receivetransducers 96. In another embodiment, the arrays 92 do not scatterradial beams directly towards transducers, but the radial waves arescattered by arrays 92 so that the waves are directed perpendicularly tothe arrays 104, allowing the arrays 104 and associated transducers 106to be used for transmission or reception of the radial waves. This mayremove the need for the transducers 96 where the X, Y and radialdetections are performed sequentially. The reflective elements withoutarrays 92 are spaced and angled so that the beam coherently scattered inthe right direction. The number and positioning of the reflector may beset to provide similar signal strength for different paths.

For detection with the parallel wave patterns, different acoustic pathscorrespond to different path lengths from the transmit transducer 100 tothe receive transducer 106. The different path lengths result indifferent delay times of an acoustic signal on one path relative to anacoustic signal on another path. For example, a short tone burst (e.g.˜5 usec) from a transmit transducer 100 results in a much longer signalat the receive transducer (e.g. ˜200 usec) due to the burst being routedalong a plurality of acoustic paths. When no touch is present, thecontroller stores a reference wave form. Comparison with the referencewave form indicates the delay and associated path corresponding to anyattenuation when a touch occurs.

For two simultaneous touches (solid circles), the acoustic waveamplitude is attenuated for four acoustic paths in the two parallelpatterns. The received signals at corresponding delay times are reduced.From the delay times of signal reductions, the X coordinates and the Ycoordinates of the two touches are determined, but there is anambiguity. The dashed circles represent possible touch locations usingthe same four acoustic paths. The radial acoustic pattern generated bythe radial transducer 91 is used to resolve the ambiguity. Onlyintersections of attenuated X and Y beams that also correspond to anattenuated radial beam correspond to true touch locations. There are noattenuated radial beams corresponding to the dashed circles.

FIG. 20 represents addition of further radial patterns generated byadditional radial transducers 91 relative to FIG. 19, according to aspecific embodiment. Three more sets of transmit radial transducers,receive transducers, and radial reflective arrays are provided. In FIG.20, the radial reflective arrays shown are not merged (like the radialreflective array 92 shown in the embodiment of FIG. 19) but are distinctarrays. The radial reflective arrays 92 in FIG. 20 are shownschematically as gray areas without the reflective elements beingexplicitly shown. A radial pattern terminating or originating at eachcorner is provided. In alternative embodiments, only two radialpatterns, or three or more than four radial patterns may be used. Radialpatterns originating or terminating at locations other than the cornersmay be used (an example is shown in FIG. 17). In other embodiments, onlythe radial patterns without the X and Y (horizontal and vertical)patterns are provided, such as seen in FIG. 23.

Due to the positioning of the reflectors and/or transducers, there maybe one or more radial lines along which detection is not performed for agiven radial wave pattern, such as represented by the region between thetwo dashed radial lines seen in FIG. 20. The X and Y detection is ableto detect the center or other location that may be a blind spot commonto detection based on all the radial patterns. For other locations(e.g., non-center locations), even if detection based on one of theradial patterns provides a blind spot, detection based on the other orremaining radial patterns may be used to resolve location. In theembodiment shown in FIG. 20, six different sources of locationinformation are provided (X, Y, and four angles).

Acoustic waves from two different radial patterns are received at eachof the radial reflective arrays. The difference in angle of incidence isused to direct the acoustic energy to the appropriate receivetransducer. The reflectors are angled and spaced to reflect the acousticenergy of one radial pattern a first direction and other reflectors areangled and spaced to reflect the acoustic energy of the other radialpattern in a second, opposite direction. For any given location in thearray, the acoustic energy from the two different radial patternsarrives or leaves at a different angle. The reflectors are superposed,that is, combined into one array area without overlapping reflectiveelements at different orientations. Alternatively, separate arrays in aside-by-side arrangement are provided, such as discussed above for thearrays of the parallel pattern with the arrays for the radial pattern.In yet other alternatives, the reflectors for the parallel pattern maybe superposed or arranged in a same line or array with the arrays forone or more radial patterns.

For use of the touch sensor on a screen, the transducers and reflectivearrays are on the same surface of the substrate as the touch region.FIGS. 18-20 show arrangements with all the components on the topsurface. For grating transducers, the piezoelectric may be on the backside. To protect and hide the transducers and associated wiring, thetouch sensor is assembled, such as for a touchscreen, with arrays andtransducers on the front substrate surface covered by a protective bezelin the final product of which the touch sensor is a component. The bezelcovers the top surface-mounted components of the touch sensor outside ofthe touch region in the complete product. These components are shownlarger than needed for description herein. The transducer sizes andarray widths are exaggerated relative to the dimensions of the touchregion for clarity. The transducer and arrays may be on a 20 mm or lessmargin of the touch sensor.

It is noted that some embodiments of touch sensors may have bottomsurface-mounted transducers and arrays, eliminating the need for anybezel on the finished product. For example, FIG. 21 shows a touch sensorfor use with a zero-bezel final product. A triangular substrate andtouch surface is shown in this example, but rectangular or other shapesmay be used. Triangular is shown to more simply represent thepropagation of the surface acoustic waves. In FIG. 21, the solid raysrepresent propagation on a top surface for touch detection. The dashedrays represent propagation on a bottom surface. The arrays of reflectorsand transducers positioned on the back of the substrate are also shownin dashed lines. This arrangement allows the entire top surface to befree of any obstructions while placing all arrays and transducers thatneed protection on the back side of the substrate, hence permitting afinal assembled product with no bezel. In other embodiments some, butnot necessarily all, arrays and transducers are located on the backside.

The connecting surfaces between the top and bottom surfaces of thesubstrate are rounded. The surface acoustic waves generated on thebottom surface are directed towards and then travel over the roundedconnecting surface, and propagate over the touch region, which may bepart of or the entire top surface and/or the connecting surfaces.Similarly, the surface acoustic waves that travel through the touchregion travel over another connecting surface and to the radialreflective arrays and/or receive transducers on the bottom surface. Theperipheral edge of the substrate may be straight or curved along thecircumference, such as straight as shown in FIG. 21 or curved as shownin FIG. 12. In alternative embodiments, one or more reflectors and/ortransducers could be positioned at the periphery or on the top surface.

In other embodiments, edge waves are used for transmitting or receiving.For example, the edge wave array of periodic perturbations described inU.S. Published Application No. 2005/0243071, which is incorporated byreference, may be used.

In yet other embodiments, sputtered, printed, or PVDF interdigitaltransducers positioned along all of or part of an edge are used fortransmission or reception of surface acoustic waves. The interdigitaltransducers are positioned to generate the desired surface acousticwaves in a continuum or at multiple locations adjacent to the touchregion.

The number of transducers may be reduced by using reflectors. Forexample, a series of reflectors reflect the surface acoustic waves alongthe same or different direction of travel. The reflectors may bepositioned so that the same transducer acts as both transmitter andreceiver. The surface acoustic waves are generated, pass over the touchregion, and are then reflected back to the same transducer.

FIG. 23 shows another example layout where two radial transducers 91(shown as grating transducers) are in two corners of the touch surface.For one of the radial transducers 91, two transducers A and B areprovided with radial reflective arrays 106 and 108, respectively, alongedges opposite the radial transducer 91. For the other of the radialtransducers 91, two transducers C and D are provided with radialreflective arrays 110 and 112, respectively, along edges opposite theradial transducer 91. In sequential operation, the transducers A and Cand the transducers B and D may be connected to a same pulse generator,controller or sensor channel.

In one embodiment, the radial transducer(s) used are gratings (such asshown in FIG. 13) etched onto a front surface of the glass or substratein one or more corners. The piezoelectric block is positioned oppositethe grating on the back surface. Along two or more edges, interdigitaltransducers are positioned on the back surface. The interdigitaltransducers extend along most or all of the edge for transmitting orreceiving acoustic energy along a line or edge. The interdigitaltransducer structure may either be excluded from the locations of thepiezoelectric blocks, or the piezoelectric block may be placed furtherfrom the substrate edge than the interdigital transducer structure, oralternatively the piezoelectric blocks for the radial transducers may bepositioned over of the interdigital transducers so that the compressionwave from the piezo blocks travels through the interdigital transducersan through the glass.

Other layouts with any combination of radial, parallel, or otherpatterns may be used. Various locations in the touch region areintersected by acoustic paths from different directions, allowingdetermination of location. By providing a sufficient number of acousticpaths or patterns, multiple touches may be detected and thecorresponding locations determined.

FIG. 22 shows a general method for detecting a touch on a surface. Themethod is implemented using the touch sensors, layouts, and/or radialtransducers discussed above or different touch sensors, layouts, and/ortransducers. Additional acts may be provided.

In act 112, an acoustic fan is generated. The fan is generated assurface acoustic waves. Other types of acoustic waves may be used. Apiezoelectric element or film generates longitudinal, shear or otherwaves. The waves are converted to surface acoustic waves or useddirectly.

The fan has non-parallel edges over the surface in an area for thetouch. A radial transducer and/or reflectors cause the acoustic beam tofan out or diverge. Any range or arc of the fan may be generated, suchas 45° or more. The opposite, side edges of the fan diverge at an angleof 45° or more. A converging fan may be generated, such operating in areceive rather than a transmit mode. By reversing the direction ofpropagation, a converging fan is created. The fan beam is generateddirectly, such as with a radial transducer. Alternatively, the fan beamis generated indirectly, such as by reflection or lensing from a linearbeam.

In act 114, an angle associated with a touch is detected. The temporalprofile of the received acoustic energy is compared to a referenceprofile. The location with attenuation is identified from thecomparison. The delay associated with location on the profile indicatesthe acoustic path along which the touch occurred. In a polar coordinatesystem of a fan beam, the acoustic path corresponds to an angle.

For determining the angle, the acoustic path timing accounts for anyreflections, such as the reflection of acoustic energy by radialreflective arrays from different radial beams to a receive transducer.The radial beam or angle associated with attenuation in the acoustic fanis determined from the timing. By determining the timing associated withthe attenuation over the complete path, the acoustic path may bedetermined. Without the radius along the acoustic path being determinedfrom one measurement, the angle associated with the attenuation isdetermined without resolution of the point location of the touch. Inalternative embodiments, attenuation is determined along a given pathwhere the path represents a collection of points, such as a pair of linesegments, rather than a simple radial line. For example, a path may bereflected or otherwise be associated with all the locations along anynon-straight path. The timing of the attenuation is used to determinethe path and corresponding possible locations of the touch.

Radial transducers may be used to detect radius along a radial line atwhich a touch occurs. The angle or radial is detected by timingassociated with attenuation. The radius along the radial is detected bywidth of the attenuation. Referring to FIGS. 24 and 25, detecting radiusis shown. The location 90 of the touch is shown closer to the radialtransducer 91 in FIG. 24 than in FIG. 25. The location 90 of the touchis at a different radius in FIG. 24 than FIG. 25, but along a sameradial or at a same angle φ relative to the radial transducer 91. Theangle is detected by the timing of attenuation in the received signal.The reflectors 92 redirect the surface acoustic waves to the transducer96. Since the surface acoustic waves at different angles traveldifferent distances to get from the radial transducer 91 to the receivetransducer 96, a waveform 200, 202 of surface acoustic wave amplitudeover time is generated. The attenuation at a particular point along thewaveform 200, 202 indicates the angle. The attenuation is represented asthe dip or notch in the waveform 200, 202. A shadow is observed in thereceived signal at the transducer 96, and the mean time delay associatedwith the attenuated signal determines the touch coordinate angle φ. Thecenter of the shadow or attenuation notch occurs at the same time,indicating the same angle in both examples of FIGS. 24 and 25.

The radius along the radial of the location 90 of the touch results infurther differences in the waveform 200, 202 received at the transducer96. The width or duration of the signal attenuation due to the touch isdifferent depending on the radius. The duration of the notch orattenuation is longer for touches closer to the radial transducer 91(see FIG. 24) and shorter for touches further from the radial transducer91 (see FIG. 25). The duration of the touch induced attenuation (i.e.,width of the notch) in the waveform 200, 202 the received transducer 96provides information about the radial distance between the location 90of the touch and the radial transducer 91. By detecting the duration orwidth of attenuation, the radius of the location is determined.

There is some ambiguity between a touch with a larger substrate surfacecontact area further from the radial transducer 91 and a touch withsmaller contact area closer to the radial transducer 91. In the layoutof FIG. 19, for example, this ambiguity may at least partially beresolved by determining the contact area from touch shadow strengthsobserved in the X and Y signals received by the transducers 106. Inother layouts, other surface acoustic wave measurements, such as fromother angles or directions, may be used to resolve the size ambiguity.The size determined from the width in other measurements is averaged,selected or combined to provide a width perpendicular to the detectedangle φ. Given this width of the contact area, the radius along theradial is determined by the width in the waveform 200, 202. A lookuptable, mathematical function, or other process correlates the width inthe waveform 200, 202 with the radius given a size of contact.

In addition or as an alternative to the radius determined by the widthof the attenuation, a measure of total touch signal strength (e.g. SAWattenuation integrated over angle φ) may be used to determine positionsof multiple simultaneous touches. For example, referring to FIG. 19, ifthe total signal strength of the upper right touch is measured using Xand Y signals from transducers 106 is used to determine the touch size,and this touch size is used with the total signal strength from theradial signal from radial transducer 91 to receive transducer 96, theradius of the touch may be determined. If this radial depth isconsistent with the (x,y) coordinates from the X and Y signals, then thetouch location is confirmed. If not, a false association of shadows isrejected. Hence the extra radius information provides an additionallevel of redundancy resolve ambiguities. This added information toresolve ambiguities becomes more valuable with larger numbers ofsimultaneous touches even if of limited usefulness in the simple twotouch case illustrated in FIG. 19,

In act 116, the point location is determined. To resolve ambiguity forthe point location of the touch, an additional pattern of acousticenergy is generated. For example, another acoustic wave fan propagateson the surface. The other acoustic fan traverses the surface in adifferent direction, such as from a different angle.

The transmitting of different fan beams or sensing along differentpatterns of paths occurs sequentially. After an acoustic pulse traversesalong one pattern, another acoustic pulse is generated for anotherpattern. The patterns are used sequentially. In alternative embodiments,the detection maybe performed along one pattern more frequently thananother. In yet other embodiments, simultaneous detection may be used,such as by simultaneous excitation of more than one transmit transducerand either design. If the acoustic design of the touch sensor is notsufficiently clean to avoid cross-talk between simultaneously measuredsignals, effects of acoustic cross-talk may be reduced by a variety ofmethods including use of coded pulses.

By having two fan beams propagating from different directions, a pointlocation may be determined. The angle for each defines a line on thesurface. The intersection of the acoustic paths or lines defines thepoint location. The point location is any size point, depending on theresolution of the touch sensor. The point may correspond to an area, butis an area associated with a touch. The use of “point” is to distinguishfrom the line or angle that may be determined for a touch that extendsbeyond the region of actual touching.

As another example for determining a point location, a parallel beampattern is generated in addition to at least one radial pattern. Thetouch is detected along one of the parallel acoustic paths. Since theacoustic paths of the parallel pattern intersect the paths of the radialpattern from different directions for each possible location, thelocation may be detected.

In yet another example, two different parallel patterns are generated inaddition to at least one radial pattern. In one embodiment, the parallelpatterns are perpendicular to each other (e.g., X and Y). By detectingthe touch or touches along perpendicular paths, a point location of thetouch or touches may be determined by the parallel patterns inconjunction with the radial pattern(s).

By providing for three or more acoustic paths to be detected for eachtouch, two or more touch locations occurring at a same time may benon-ambiguously determined. For example, two touches occur at a sametime. The two touches are along the same or different radial withrespect to a given fan beam. The detection based on the fan beam eitherindicates one angle for the two touches or indicates two angles for thetwo touches. By using one or more angles detected from another fan beam,a X location from a parallel pattern, a Y location from a parallelpattern, or combinations thereof, the two point locations aredetermined.

In act 116, the point location of one or more touches is determined as afunction of the angle for the fan beam. Another acoustic path is used todetermine the point location. The intersection of two different acousticpaths associated with attenuation indicates the point location of thetouch. For multiple touches, the intersection of three or more differentacoustic paths provides one location and the intersection of three ormore other acoustic paths provides another location.

The point location is determined by an attenuated signal at theintersection of two radial beams, each from different radial patterns.Alternatively, the point location is determined at the intersection of aradial beam (angle) and one or more acoustic paths from respective oneor more parallel patterns. In one embodiment, four angles, a Y location,and a X location are used to determine the touch location. Three or moreacoustic paths for each touch may allow determination of two toucheswithout ambiguity due to multiple attenuations being received by a sametransducer. Sufficient patterns are provided to account for any blindspots for one or more of the patterns.

In any of the embodiments discussed above, the surface acoustic wavesmay be Rayleigh or quasi-Rayleigh waves. Ultrasonic touch sensors usingplate waves and Love waves rather than Rayleigh waves may be used insome embodiments. For example, a convex wedge transducer may be used togenerate waves in any acoustic mode.

The above description is intended to be illustrative, and notrestrictive. The above-described embodiments (and/or aspects thereof)may be used in combination with one another. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from its scope.Dimensions, types of materials, orientations of the various components,and the number and positions of the various components described hereinare intended to define parameters of certain embodiments, and are by nomeans limiting and are merely exemplary embodiments. Many otherembodiments and modifications within the spirit and scope of the claimswill be apparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

The invention claimed is:
 1. A touch sensor for detecting a touch, thetouch sensor comprising: a touch substrate having a top surface and abottom surface, the top surface having a touch region; a firsttransducer configured to: generate or receive first surface acousticwaves on the touch region, the first transducer comprising a firstradial transducer; and a second transducer configured to: receive orgenerate the first surface acoustic waves; detect a first angleassociated with the touch from attenuation of the first surface acousticwaves along a first radial line; determine a point location of the touchas a function of the first angle; and determine a radius of the touchalong the first radial line, the radius determined as a function of awidth of attenuation, wherein the first surface acoustic waves have afirst radial pattern, generated via refraction by the first radialtransducer, with an angular span of at least 20° in the touch region,the first radial pattern comprising a first plurality of linear beamscomprising an amplitude above a predefined threshold across a width ofthe beams, the first radial pattern being divergent as a distance fromthe first transducer increases.
 2. The touch sensor of claim 1 whereinthe first transducer is on the top surface.
 3. The touch sensor of claim1 further comprising a first radial reflective array comprising aplurality of reflective elements, the reflective elements beingdifferently angled and positioned to reflect the first surface acousticwaves from the first radial pattern to substantially one direction tothe second transducer.
 4. The touch sensor of claim 1 wherein the firsttransducer is on the bottom surface, and the top and bottom surfaces arecoupled via a rounded connecting surface of the touch substrate.
 5. Thetouch sensor of claim 1 wherein the first radial transducer comprises aradial wedge transducer.
 6. The touch sensor of claim 1 wherein theangular span comprises at least 45°.
 7. The touch sensor of claim 1wherein the angular span comprises at least 90°.
 8. The touch sensor ofclaim 1, further comprising: a third transducer for generating secondsurface acoustic waves on the touch region, the second acoustic wavesintersecting in the touch region the first surface acoustic waves, thesecond surface acoustic waves have a second radial pattern comprising asecond plurality of linear beams comprising an amplitude above thepredefined threshold across a width of the beams, wherein the touchregion is rectangular, further comprising a fourth transducer, a firstlinear reflective array and a second linear reflective array, the thirdtransducer and first linear reflective array transmitting the secondsurface acoustic waves in a first parallel pattern across the touchregion and being received by the second linear reflective array and thefourth transducer.
 9. The touch sensor of claim 8 further comprising afirst radial reflective array positioned along a first edge of the touchregion, the first radial reflective array for reflecting the firstsurface acoustic waves in the first radial pattern at least to thesecond transducer.
 10. The touch sensor of claim 9 further comprising asecond radial reflective array, a third radial reflective array, and afourth radial reflective array positioned along, respectively, second,third and fourth edges of the touch region.
 11. The touch sensor ofclaim 9 further comprising fifth and sixth transducers and third andfourth linear reflective arrays, the fifth transducer and third linearreflective array for transmitting third surface acoustic waves in asecond parallel pattern across the touch region, the second parallelpattern perpendicular to the first parallel pattern such that the thirdsurface acoustic waves are received by the fourth linear reflectivearray and the sixth transducer, wherein the fourth transducer detects aX position of the touch and the sixth transducer detects a Y position ofthe touch.
 12. The touch sensor of claim 10 further comprising fifth andsixth transducers and third and fourth linear reflective arrays, thefifth transducer and third linear reflective array for transmittingthird surface acoustic waves in a second parallel pattern across thetouch region, the second parallel pattern perpendicular to the firstparallel pattern such that the third surface acoustic waves are receivedby the fourth linear reflective array and the sixth transducer, whereinthe fourth transducer detects a X position of the touch and the sixthtransducer detects a Y position of the touch; and further comprising aseventh transducer and an eighth transducer, the seventh transducer fortransmitting fourth surface acoustic waves in a second radial patternintersecting the first radial pattern, the first and seventh transducerspositioned at different corners of the touch region, and the eighthtransducer and fourth radial reflective array receiving the fourthsurface acoustic waves.
 13. The touch sensor of claim 8, wherein thethird transducer comprises a radial transducer such that the secondsurface acoustic waves have a radial pattern in the touch region.
 14. Amethod for detecting a touch on a surface, the method comprising:generating a first acoustic fan with non-parallel propagation over thesurface in an area for the touch; detecting a first angle associatedwith the touch from attenuation of the first acoustic fan along a firstradial line; determining a point location of the touch as a function ofthe first angle; and determining a radius of the touch along the firstradial line, the radius determined as a function of a width ofattenuation, wherein generating the first acoustic fan comprisesgenerating, via refraction by a first radial transducer, a first fanbeam of surface acoustic waves.
 15. The method of claim 14 wherein theangular span of the first acoustic fan being at least 45°.
 16. Themethod of claim 14 wherein detecting the first angle comprisesreflecting acoustic energy from the first radial line of the firstacoustic fan, and determining a timing of the attenuation in theacoustic energy for the first radial line associated with the touch. 17.The method of claim 14 further comprising: generating a second acousticfan propagating on the surface from different directions than the firstacoustic fan; detecting a second angle associated with the touch fromattenuation of the second acoustic fan along a second radial line; andwherein determining the point location comprises determining anintersection of the first radial and the second radial line.
 18. Themethod of claim 14 further comprising: detecting the touch along a firstone of a plurality of first parallel acoustic paths in a firstdirection; and detecting the touch along a second one of a plurality ofsecond parallel acoustic paths in a second direction perpendicular tothe first direction; wherein determining the point location comprisesdetermining an intersection of the first and second acoustic paths andthe first radial line.
 19. The method of claim 17 further comprising:detecting an additional touch occurring at a same time as the touch, theadditional touch detected along the second radial line; and determiningan additional point location of the additional touch as a function ofthe second radial line; wherein the point location and additional pointlocation are determined without ambiguity due to multiple attenuationsbeing received by a same transducer.
 20. A touch sensor comprising: asubstrate; a first radial transducer on the substrate, the first radialtransducer configured to: generate or receive first surface acousticwaves on the substrate along different radial lines separated by anangle of at least 20° in a touch region, the first surface acousticwaves comprising a first plurality of linear beams comprising anamplitude above a predefined threshold across a width of the beams; andone or more first receive transducers operable to receive the firstsurface acoustic waves along the different radial lines; a secondtransducer on the substrate, the second transducer configured to:generate or receive second surface acoustic waves on the substrate alongparallel lines; a first linear reflective array configured to reflectthe second surface acoustic waves from the second transducer in aparallel pattern in the touch region; and one or more second receivetransducers configured to receive the second surface acoustic waves fromparallel pattern; wherein the touch sensor is configured to: detect afirst angle associated with a detected touch, on a surface of thesubstrate, from attenuation of the first surface acoustic waves along afirst radial line; determine a point location of the touch as a functionof the first angle; determined a radius of the touch along the firstradial line, the radius determined as a function of a width ofattenuation; wherein the first surface acoustic waves have a firstradial pattern generated via refraction by the first radial transducer.21. The touch sensor of claim 20 further comprising: a first radialreflective array having reflective elements positioned to reflect thefirst surface acoustic waves in a radial pattern, the reflectiveelements being at different angles on the substrate and havingnon-uniform spacing.
 22. The touch sensor of claim 1, wherein the firsttransducer and the second transducer are comprised of a same radialtransducer.
 23. The touch sensor of claim 1, wherein the widthcorresponds to a detected time duration of the attenuation.
 24. Themethod of claim 14, wherein the width corresponds to a detected timeduration of the attenuation.
 25. The touch sensor of claim 20, whereinthe width corresponds to a detected time duration of the attenuation.26. The touch sensor of claim 1, wherein the radius comprises a distancebetween the first transducer and the determined point location of thetouch along the first radial line.
 27. The method of claim 14, whereinthe radius comprises a distance between a transducer and the determinedpoint location of the touch along the first radial line.
 28. The touchsensor of claim 20, wherein the radius comprises a distance between thefirst radial transducer and the determined point location of the touchalong the first radial line.